Cold starts

LeVeL

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Late January, 4:45am, 10 degrees outside (-12C). Car's been sitting outside for ten hours. It's facing a 1.5mi trip to the gym where it will be shut off for an hour, then driven the 1.5mi back home and shut off again for an hour, before finally being driven 12mi to work.

Are these frequent cold starts and short initial drives bad? If so, why? All I can think of is the extra toll on the starter and maybe on the battery; condensation in the oil (how long does that take to burn off?); possibly running rick; not sure if the engine faces extra wear since 1.5mi isn't as short as just backing out of the driveway. What can be done to lessen the stress of doing this daily, year-round?
 
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GRtak

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Yes. There are a few things that are bad about this, but I want to know why running Rick is bad? :p

As you point out, the condensation is not good. More importantly, until the engine gets warm, it is not sealing properly. There is a ton of blow by that causes acids to form in the oil. Acid is not a fun trip for the engine.

Why not ride a bike there? You are already going to work out, so do a bit more there and back.

Or, drive to get your coffee so the engine has a chance to warm up and get rid of the nasty stuff.
 

avanti

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Jog to the gym, perfect warm up, kill two birds with one stone!

Your welcome.
 

LeVeL

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Yes. There are a few things that are bad about this, but I want to know why running Rick is bad? :p
Freudian slip :wicked:


As you point out, the condensation is not good. More importantly, until the engine gets warm, it is not sealing properly. There is a ton of blow by that causes acids to form in the oil. Acid is not a fun trip for the engine.
Won't the engine get rid of the condensation and acids on the longer drive to work?


Why not ride a bike there? You are already going to work out, so do a bit more there and back.
Jog to the gym, perfect warm up, kill two birds with one stone!

Your welcome.
I don't really want to run or bike down icy poorly lit roads <_<
 

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I think one problem with cold start is that the lubricating properties of oil aren't the best if it's cold, if I'm not mistaken. So the engine would need to run and warm up for few seconds for the oil to distribute properly.

Currently both out cars get cold started and driven for 5-10 minutes at least twice a day for the whole winter. We have solved the situation by just using cheap cars that are nearer the end of their lifespan anyway, cold started or not. Also, I try to drive each car a bit longer once in a few weeks to let the battery charge up properly.
 
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93Flareside

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If you let the car warm up for 30 minutes (or time how long it takes before the temp gauge starts to move) on both sides of your trips, it shouldn't be a problem. Basically, just enough to get the condensation to burn off.
 

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How much extra wear is half an hour of cold idling - quite a slow way of putting heat into your engine - going to cause?
 

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Cold starts

It's better that way imo to let all the metal warm slowly to avoid shock and possibly crack something. The amount of wear associated is less than what you'd get from immediately taking up the revs and introducing more heat at a faster rate and forcing metal to expand faster.

I liken it to boilers. You can't put a whole bunch of heat in when it's cold because you'll crack tubes and cause leaks. If you warm it slowly until you either start making steam(on low pressure systems) or are over 110 degrees Fahrenheit(on warm water systems) everything's typically warmed up enough to handle larger amounts of heat. With high pressure steam, if you cannot hold your hand on plumbing caps, then it's ready to roll.
 
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narf

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Imo you'll run overly rick for way too long, washing oil off your cylinder walls and thereby increasing wear massively. With the low amount of heat generated per revolution when idling, you'll prolong that hard-wearing operation unnecessarily long.


Someone else's opinion:

 
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prizrak

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Cold starts

Agree with narf here, it's worse to idle while running rich than it is to give it a minute and then drive normally. The only advise I have is to keep the revs low until after the engine warms up enough (usually couple of minutes after you see water temp in the middle)

Also if your oil is synthetic you shouldn't have too much worry about cold lubrication, those compounds are quite good at staying liquid.
 

93Flareside

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Cold starts

You mean to tell me that the car doesn't use O2 and mass air and temp sensors to ensure that it doesn't run poorly? It just operates on a "good enough" base curve without taking any real world info into consideration when it's cold? I call bullshit.

Yes, in sure it has a cold start under x degrees starting set up but, it's nothing horrible that would damage anything.

But, if you're thinking starting a car and immediately going on your way and shutting the car off before it fully warms up is ok, that's your deal. Every single time you start there's microscopic wear before oil can hit everything. There's still residual, much less if it sits for a week and probably none after a month. But, day to day use, there should still be enough oil to not cause catastrophic wear.

We go through this every year. Basically it comes down to, do what you want. It ain't my car.
 
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GRtak

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The O2 senesors need to be about 600F before they star to work properly. The MAF sensor will help get the fuel ratio close, but the O2 are the lie detector to them.


On the acids. The way I was taught, once the acids are there, they don't go away.
 

93Flareside

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Cold starts

Then all of my cars should have had major blow by and consume stupid amounts of oil. So far, that's not happened. If you don't either, then I guess we're both right. Also, how long do you think it takes for 600F to hit the O2 sensor that are how close again to the headers? It doesn't take that long for them to start reporting data.


Furthermore, multi-wire (over 2) are heated O2 sensors so that they can heat up as quick as possible for the ECU to receive data.
 
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prizrak

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You mean to tell me that the car doesn't use O2 and mass air and temp sensors to ensure that it doesn't run poorly? It just operates on a "good enough" base curve without taking any real world info into consideration when it's cold? I call bullshit.

Yes, in sure it has a cold start under x degrees starting set up but, it's nothing horrible that would damage anything.

But, if you're thinking starting a car and immediately going on your way and shutting the car off before it fully warms up is ok, that's your deal. Every single time you start there's microscopic wear before oil can hit everything. There's still residual, much less if it sits for a week and probably none after a month. But, day to day use, there should still be enough oil to not cause catastrophic wear.

We go through this every year. Basically it comes down to, do what you want. It ain't my car.
Of course all of those can and do tune how the car behaves but any EFI car is set to run rich until it gets to a certain point. Think back to carbureted engines with choke, you would richen up the mixture on warm up. That EE video up there does a pretty good job explaining it. Short drives are not ideal but idling on a cold engine is not great either.
 

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You mean to tell me that the car doesn't use O2 and mass air and temp sensors to ensure that it doesn't run poorly? It just operates on a "good enough" base curve without taking any real world info into consideration when it's cold? I call bullshit.
You need to go pick up a manual on EFI. Yes, an EFI vehicle operates in open loop (ignoring the O2 sensor) off a base fuel map while warming up. It only goes into feedback mode once it reaches a certain critical engine coolant temperature *and* the O2 sensors are warmed up enough to start providing valid feedback. The car cannot and will not make any feedback-based changes in this mode and will deliberately run rich.
 

LeVeL

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But, if you're thinking starting a car and immediately going on your way and shutting the car off before it fully warms up is ok, that's your deal.
I think it's pretty well established that it's not good to let the car idle for a long time to warm up and that it's far better to let it run for 30-60 seconds and then just start driving (taking it easy until it fully warms up). What I'm wondering here is whether or not it's bad to drive for only 1.5-2 miles, shut it off for an hour, drive another 1.5-2 miles, shut it off for another hour, and then drive it longer and let it fully warm up - will those two short drives make a difference or no? Again, the car will be fully warmed up for the third, longer drive.
 

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And how long is that exactly?
Varies by maker and model. On my Series III, to use something I'm familiar with, it doesn't go into closed loop until 80 degrees C engine coolant temperature. My 87 was among the first to have a heated oxygen sensor so technically that's ready in about 30 seconds to 3 minutes, but the engine still needs cold start enrichment beyond that time period ('choke' if you will) so it (like many cars) won't go into closed loop until the engine is warm enough that it doesn't need cold start enrichment any more.

- - - Updated - - -

Should also mention that General Motors (who is really good at collecting statistics but really bad at applying them) did multiple studies over several decades and determined that the best cold start strategy to prolong the life of your engine is to start the car, wait 30 seconds, then drive off briskly but not abusively. Better still is to then get on the highway and drive ten miles at highway speeds (the last time they did this, highway speed was defined as 'about 65mph').

- - - Updated - - -

I think it's pretty well established that it's not good to let the car idle for a long time to warm up and that it's far better to let it run for 30-60 seconds and then just start driving (taking it easy until it fully warms up). What I'm wondering here is whether or not it's bad to drive for only 1.5-2 miles, shut it off for an hour, drive another 1.5-2 miles, shut it off for another hour, and then drive it longer and let it fully warm up - will those two short drives make a difference or no? Again, the car will be fully warmed up for the third, longer drive.
That's very bad and it does make a negative difference. 2 miles is not enough to get many cars up to operating temperatures.

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The O2 senesors need to be about 600F before they star to work properly. The MAF sensor will help get the fuel ratio close, but the O2 are the lie detector to them.


On the acids. The way I was taught, once the acids are there, they don't go away.

Some of them do 'boil off' or are otherwise expelled from the oil by heat along with the water (condensation) that will naturally appear in oil in an engine.
 

93Flareside

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Cold starts

Ok, so what's the big deal of warming the car until the temp gauge moves? At that point heat works so you defog/frost everything.
 
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